1. Field of the Invention
The presently disclosed subject matter relates to an endoscope, and more particularly, to an endoscope in which an observation window can be cleaned by jetting a cleaning fluid from a nozzle.
2. Description of the Related Art
There has been known an endoscope including a cleaning nozzle at a distal end part thereof, in which a cleaning liquid (such as water) and a gas (such as air and carbon dioxide gas) are jetted from the cleaning nozzle toward an observation window, to thereby enable cleaning of the observation window.
Japanese Patent Application Laid-Open No. 03-165731 describes a technology concerning such an endoscope including the cleaning nozzle, in which a convex portion is provided between the observation window and the cleaning nozzle, to thereby distribute the cleaning liquid to all over the surface of the observation window.
In addition, Japanese Patent Application Laid-Open No. 2003-210388 describes a technology in which the observation window is formed so as to protrude by a predetermined amount from an end surface of the distal end part, a peripheral edge of the observation window is formed so as to be inclined, and the cleaning liquid is jetted from the cleaning nozzle toward the inclined peripheral edge of the observation window.
In addition, Japanese Patent Application Laid-Open Nos. 2006-314459, 2006-320366, 2006-320367, and 2008-86664 each describe a technology in which the end surface of the distal end part on which the observation window is placed is formed in a stepwise manner, an inclined surface is formed in a wall part between respective adjacent two steps, and the cleaning liquid is jetted from the cleaning nozzle toward the inclined surfaces.